As of the end of 2004, an estimated 39.4 million people worldwide were living with HIV/AIDS, and the Centers for Disease Control and Prevention (CDC) estimate that 850,000 to 950,000 U.S. residents are living with HIV infection (UNAIDS/WHO AIDS epidemic update, December 2004; Fleming, P. L. et al. HIV Prevalence in the United States, 2000. 9th Conference on Retroviruses and Opportunistic Infections, Seattle, Wash., Feb. 24-28, 2002. Abstract 11). Although new infections have decreased in recent years, an estimated 4.9 million new HIV infections occurred worldwide during 2004 and approximately 40,000 new HIV infections occur each year in the United States.
HIV entry within the target cells involves a series of molecular events. The three main steps of virus entry within the cell are: (i) attachment of the virus to the host cells; (ii) interaction of the virus with the co-receptors; (iii) fusion of the virus and host cell membranes. Considering the complexity of the molecular events involved in viral infection, all three of these steps have been considered for the drug design of HIV entry inhibitors. The T-lymphocyte cell surface protein CD4 is the primary receptor involved in the interaction with the viral glycoprotein gp120, but a cellular co-receptor is also needed for the successful entry of the virus within the cell. At least two types of such co-receptors have been identified so far, both of which are chemokine receptors. These chemokine receptors are therefore gateways for HIV entry, determinants of viral tropism and sensitivity.
Chemokines are a superfamily of small, secreted cytokines that induce, through their interaction with G-protein-coupled receptors, cytoskeletal rearrangements and directional migration of several cell types (Butcher, et al. (1999) Adv Immunol 72: 209-253; Campbell and Butcher (2000) Curr Opin Immunol 12: 336-341; Zlotnik and Yoshie (2000) Immunity 12: 121-127). The chemokine receptor, CXCR4, is known in viral research as a major coreceptor for the entry of T cell line-tropic HIV (Feng, et al. (1996) Science 272: 872-877; Davis, et al. (1997) J Exp Med 186: 1793-1798; Zaitseva, et al. (1997) Nat Med 3: 1369-1375; Sanchez, et al. (1997) J Biol Chem 272: 27529-27531). T Stromal cell derived factor 1 (SDF-1) is a chemokine that interacts specifically with CXCR4. When SDF-1 binds to CXCR4, CXCR4 activates Gαi-protein-mediated signaling (pertussis toxin-sensitive) (Chen, et al. (1998) Mol Pharmacol 53: 177-181), including downstream kinase pathways such as Ras/MAP Kinases and phosphatidylinositol 3-kinase (PI3K)/Akt in lymphocyte, megakaryocytes, and hematopoietic stem cells (Bleul, et al. (1996) Nature 382: 829-833; Deng, et al. (1997) Nature 388: 296-300; Kijowski, et al. (2001) Stem Cells 19: 453-466; Majka, et al. (2001) Folia. Histochem. Cytobiol. 39: 235-244; Sotsios, et al. (1999) J. Immunol. 163: 5954-5963; Vlahakis, et al. (2002) J. Immunol. 169: 5546-5554).
Compounds targeting CXCR4 have been developed which are aimed at treatment of HIV infection. For example, U.S. Pat. No. 6,429,308 to Hisamitsu Pharmaceutical Co., Inc. discloses an antisense oligonucleotide to CXCR4 to inhibit the expression of the CXCR4 protein for use as an anti-HIV agent.
Peptide antagonists of CXCR4 receptors have also been disclosed. Tamamura et al (Tamamura, et al. (2000) Bioorg. Med. Chem. Lett. 10: 2633-2637; Tamamura, et al. (2001) Bioorg. Med. Chem. Lett. 11: 1897-1902) reported the identification of a specific peptide-based CXCR4 inhibitor, T140. T140 is a 14-residue peptide that possessed high levels of anti-HIV activity and antagonism of T cell line-tropic HIV-1 entry among all antagonists of CXCR4 (Tamamura, et al. (1998) Biochem. Biophys. Res. Commun. 253: 877-882). The compound has been altered to increase its efficacy and bioavailability by, for example, amidating the C-terminal of T-140 and reducing the total positive charges by substituting basic residues with nonbasic polar amino acids to generate TN14003, which is less cytotoxic and more stable in serum compared to T140. The concentration of TN14003 required for 50% protection of HIV-induced cytopathogenicity in MT-4 cells is 0.6 nM in contrast to 410 μM leading to 50% toxicity. U.S. Pat. No. 6,344,545 to Progenics Pharmaceuticals, Inc. describes methods for preventing HIV-1 infection of CD4+ cells with peptide fragments. U.S. Pat. No. 6,534,626 to the U.S. Department of Health & Human Services describes certain peptide chemokine variants for treating HIV infections.
Although advances have been made, inadequate absorption, distribution, metabolism, excretion or toxicity properties of peptide inhibitors have limited their clinical use. Small non-peptide drugs remain a major goal of medicinal chemistry programs in this area.
At the present time, the metal-chelating cyclams and bicyclams represent one of the few reported non-peptide molecules to effectively block CXCR4 (Onuffer and Horuk (2002) Trends Pharmacol Sci 23: 459-467.36). One of these non-peptide molecules is AMD3100, which entered clinical trials as an anti-HIV drug that blocks CXCR4-mediated viral entry (Donzella, et al. (1998) Nat Med 4: 72-77; Hatse, et al. (2002) FEBS Lett 527: 255-262; Fujii, et al. (2003) Expert Opin Investig Drugs 12: 185-195; Schols, et al. (1997) Antiviral Res 35: 147-156).
However, a clinical study showed cardiac-related side effect of AMD3100 (Scozzafava, et al. (2002) J Enzyme Inhib Med Chem 17: 69-7641). In fact, AMD3100, was recently withdrawn from the clinical trials due in part to a cardiac-related side effect (Hendrix, et al. (2004) Journal of Acquired Immune Deficiency Syndromes 37(2)). The latter was not a result of the compound's ability to block CXCR4 function, but due to its presumed structural capacity for encapsulating metals.
Other nitrogen containing bicyclic molecules have also been developed as CXCR4 antagonists. European Patent Publication No. 1 431 290 and PCT Publication No. WO 02/094261 to Kureha Chemical Industry Co., Ltd cover CXCR4 inhibitors that are potentially useful in treating various diseases including HIV infection.
U.S. Patent Publication No. 2004/0254221 to Yamamazi, et al. also provides compounds and use thereof to treat various diseases including HIV infections that are CXCR4 antagonists. The compounds are of the general formula:
in which A is A1-G1-N(R1)—; A1 is hydrogen or an optionally substituted, mono- or polycyclic, heteroaromatic or aromatic ring; G1 is a single bond or —C(R2)(R3)—; R1, R2, and R3 can be optionally substituted hydrocarbon groups; W is an optionally substituted hydrocarbon or heterocyclic ring; x is —C(═O)NH—; y is —C(═O)—; and D1 is hydrogen atom, alkyl with a polycyclic aromatic ring, or amine.
PCT Publication No. WO 00/56729 and U.S. Pat. No. 6,750,348 to AnorMED describe certain heterocyclic small molecule CXCR4 binding compounds, teaching that these are useful for the protection against HIV infection. The compounds are of the general formula:
in which W can be a nitrogen or carbon atom; Y is absent or is hydrogen; R1 to R7 can be hydrogen or straight, branched or cyclic C1-6 alkyl; R8 is a substituted heterocyclic or aromatic group; Ar is an aromatic or heteroaromatic ring; and X is specified ring structure.
PCT Publication No. WO 2004/091518 to AnorMED also describes certain substituted nitrogen containing compounds that bind to CXCR4 receptors. The compounds are described as having the effect of increasing progenitor cells and/or stem cells, enhancing production of white blood cells, and exhibiting antiviral properties. PCT Publication No. WO 2004/093817 to AnorMED also discloses substituted heterocyclic CXCR4 antagonists which are described as useful to alleviate inflammatory conditions and elevate progenitor cells, as well as white blood cell counts. Similarly, PCT Publication No. WO 2004/106493 to AnorMED describes heterocyclic compounds that bind to CXCR4 and CCR5 receptors consisting of a core nitrogen atom surrounded by three pendant groups, wherein two of the three pendant groups are preferably benzimidazolyl methyl and tetrahydroquinolyl, and the third pendant group contains nitrogen and optionally contains additional rings. The compounds demonstrate protective effects against infections of target cells by a human immunodeficiency virus (HIV).
It is an object of the invention to provide new compounds, methods and compositions for the treatment of viral infection, notably HIV.